fcarriedo/data-tmpl.html

## data-tmpl.html
<div class="msg">
  <h3>Msg</h3>
  <p>This is the message: </p>
  <p><i>{{.}}</i></p>
</div>

## index.html
<html>
<head>
  <style>
    body {font-family: helvetica;}
    #msgs .msg {float: left;}
    .msg {font-size: 8pt; color: #666; background-color: #eee; padding: 2px; border-radius: 5px; width: 200px; margin: 0px 3px 3px 0px;}
  </style>
  <script>
    window.onload = function() {
      // Create the event source
      var source = new EventSource("/stream");
      // On open/close events of the stream
      source.onopen = function () { console.log('opened..') };
      source.onerror = function () { console.log('error'); /*source.close();*/ };
      // On message handling
      var msgContainer = document.getElementById('msgs');
      source.onmessage = function (evt) {
        msgContainer.insertAdjacentHTML('beforeend', evt.data);
      }

      // Capture a specific event
      source.addEventListener('foo-evt', function(evt) {
        console.log('Got an event! : ' + evt.data);
      });
    };
  </script>
</head>
<body>
  <h1 id='title'>Server-sent events > Hello World!</h1>
  <div id='msgs'>
  </div>
</body>
</html>

## server.go
package main

import (
	"bytes"
	"fmt"
	"io"
	"net/http"
	"os"
	"strings"
	"text/template"
	"time"
)

type message struct {
	Id    int
	Event string
	Data  []string
}

var elems = []int{1, 2, 3}

// Event format that conforms to the spec as defined in:
// http://www.w3.org/TR/2011/WD-eventsource-20110208/#event-stream-interpretation
const evtMsgFormat = "" +
	"{{if .Id}}id: {{.Id}}\n{{end}}" + // optional
	"{{if .Event}}event: {{.Event}}\n{{end}}" + // optional
	"{{range .Data}}data: {{.}}\n{{end}}" + // required
	"\r\n" // Empty line delimits message (preferably '\r\n')

// Creates a new message
func newMsg(id int, evt, data string) message {
	return message{Id: id, Event: evt, Data: strings.Split(data, "\r\n")}
}

// Templates
var evtFormatTmpl = template.Must(template.New("evtTmpl").Parse(evtMsgFormat))
var dataTmpls = template.Must(template.ParseFiles("data-tmpl.html"))

func handleStream(w http.ResponseWriter, r *http.Request) {
	fmt.Println("Request to handle stream")

	// Write the event stream headers
	w.Header().Set("Content-Type", "text/event-stream")
	fmt.Fprintf(w, "retry: %d\r\n", 5000) // Retry policy: 5 sec

	for _, i := range elems {
		for _, j := range elems {
			var buf bytes.Buffer
			dataTmpls.ExecuteTemplate(&buf, "data-tmpl.html", fmt.Sprintf("some dynamic data: %d", j))
			msg := newMsg(j, "", buf.String())
			fmt.Printf("Sending: %#v\n", msg)
			sendMsg(w, msg)

			// Also send an event under certain conditions
			if i == 2 && j == 2 {
				msg = newMsg(i, "foo-evt", fmt.Sprintf("This is an event! %d", j))
				sendMsg(w, msg)
			}
		}
		time.Sleep(3 * time.Second)
	}
}

func sendMsg(w io.Writer, msg message) {
	// Apply the server sent message format
	mw := io.MultiWriter(os.Stdout, w)
	if err := evtFormatTmpl.Execute(mw, msg); err != nil {
		panic("Template couldn't be executed")
	}
	// Flush so that it gets pushed immediately to the client
	w.(http.Flusher).Flush()
}

func main() {
	http.HandleFunc("/stream", handleStream)
	http.Handle("/monitor/", http.StripPrefix("/monitor", http.FileServer(http.Dir("."))))
	fmt.Println("Server up & running in port: 8089")
	http.ListenAndServe(":8089", nil)
}
	<div class="msg">
	<h3>Msg</h3>
	<p>This is the message: </p>
	<p><i>{{.}}</i></p>
	</div>
	<html>
	<head>
	<style>
	body {font-family: helvetica;}
	#msgs .msg {float: left;}
	.msg {font-size: 8pt; color: #666; background-color: #eee; padding: 2px; border-radius: 5px; width: 200px; margin: 0px 3px 3px 0px;}
	</style>
	<script>
	window.onload = function() {
	// Create the event source
	var source = new EventSource("/stream");
	// On open/close events of the stream
	source.onopen = function () { console.log('opened..') };
	source.onerror = function () { console.log('error'); /source.close();/ };
	// On message handling
	var msgContainer = document.getElementById('msgs');
	source.onmessage = function (evt) {
	msgContainer.insertAdjacentHTML('beforeend', evt.data);
	}

	// Capture a specific event
	source.addEventListener('foo-evt', function(evt) {
	console.log('Got an event! : ' + evt.data);
	});
	};
	</script>
	</head>
	<body>
	<h1 id='title'>Server-sent events > Hello World!</h1>
	<div id='msgs'>
	</div>
	</body>
	</html>
	package main

	import (
	"bytes"
	"fmt"
	"io"
	"net/http"
	"os"
	"strings"
	"text/template"
	"time"
	)

	type message struct {
	Id int
	Event string
	Data []string
	}

	var elems = []int{1, 2, 3}

	// Event format that conforms to the spec as defined in:
	// http://www.w3.org/TR/2011/WD-eventsource-20110208/#event-stream-interpretation
	const evtMsgFormat = "" +
	"{{if .Id}}id: {{.Id}}\n{{end}}" + // optional
	"{{if .Event}}event: {{.Event}}\n{{end}}" + // optional
	"{{range .Data}}data: {{.}}\n{{end}}" + // required
	"\r\n" // Empty line delimits message (preferably '\r\n')

	// Creates a new message
	func newMsg(id int, evt, data string) message {
	return message{Id: id, Event: evt, Data: strings.Split(data, "\r\n")}
	}

	// Templates
	var evtFormatTmpl = template.Must(template.New("evtTmpl").Parse(evtMsgFormat))
	var dataTmpls = template.Must(template.ParseFiles("data-tmpl.html"))

	func handleStream(w http.ResponseWriter, r *http.Request) {
	fmt.Println("Request to handle stream")

	// Write the event stream headers
	w.Header().Set("Content-Type", "text/event-stream")
	fmt.Fprintf(w, "retry: %d\r\n", 5000) // Retry policy: 5 sec

	for _, i := range elems {
	for _, j := range elems {
	var buf bytes.Buffer
	dataTmpls.ExecuteTemplate(&buf, "data-tmpl.html", fmt.Sprintf("some dynamic data: %d", j))
	msg := newMsg(j, "", buf.String())
	fmt.Printf("Sending: %#v\n", msg)
	sendMsg(w, msg)

	// Also send an event under certain conditions
	if i == 2 && j == 2 {
	msg = newMsg(i, "foo-evt", fmt.Sprintf("This is an event! %d", j))
	sendMsg(w, msg)
	}
	}
	time.Sleep(3 * time.Second)
	}
	}

	func sendMsg(w io.Writer, msg message) {
	// Apply the server sent message format
	mw := io.MultiWriter(os.Stdout, w)
	if err := evtFormatTmpl.Execute(mw, msg); err != nil {
	panic("Template couldn't be executed")
	}
	// Flush so that it gets pushed immediately to the client
	w.(http.Flusher).Flush()
	}

	func main() {
	http.HandleFunc("/stream", handleStream)
	http.Handle("/monitor/", http.StripPrefix("/monitor", http.FileServer(http.Dir("."))))
	fmt.Println("Server up & running in port: 8089")
	http.ListenAndServe(":8089", nil)
	}